/Engine/Source/Runtime/Engine/Public/Performance/EnginePerformanceTargets.h
The maximum threshold for an 'OK' frame time in miliseconds (cosmetic onlyand used for fps/stat display, should not be used in scalability code) Values above this will be red, values between this and the acceptable limit will be yellow, and values below will be green.
static float GetUnacceptableFrameTimeThresholdMS()